Surface effect vessels which use cushions of air to reduce friction between the boat hull and the water are well known in the prior art. Basically, surface effect vessel technology involves injecting pressurized air under the hull of a boat so that at least a portion of the boat hull rides upon a cushion of air. By utilizing gas pressure contained within a pocket under the hull, a surface effect vessel can operate at higher speeds and reduced power levels as compared to conventional vessels. This increased performance is due to the fact that the friction between the air cushion and the boat hull is substantially less than the friction between the water and the boat hull. Thus, riding upon a cushion of air allows a surface effect vessel to reach higher speeds and operate more efficiently with a smaller engine than a typical vessel.
There are many prior art designs which utilize this surface effect. For examples, see U.S. Pat. Nos. 5,860,380, 5,611,294, 5,415,120 and 5,176,095 to Burg, U.S. Pat. No. 5,570,650 to Harley, U.S. Pat. No. 4,574,724 to Stolper and U.S. Pat. No. 3,968,763 to Mason, the disclosures of which are hereby incorporated by reference. One of the primary problems with these and all other prior art designs is that the water/air seal that is maintained by the displacement of the hull allows excessive amounts of air to escape. This air loss increases the volume and pressure of the air required to maintain an air cushion under the vessel. Producing and providing pressurized air requires power from the vessel's engines and blowers. Thus, the efficiency and performance of the vessel are greatly diminished when air escapes from the supporting air cushion.
Prior art surface effect vessels, such as those discussed above, further suffer from a number of other additional problems. For example, prior art surface effect vessels have a greater tendency to loose their supporting cushion of air in choppy or rough seas. As the surface effect vessel rolls in the rough seas, air in the supporting cushion tends to escape from the sides of the boat hull. In addition, air tends to escape from the supporting air cushion when the aft and bow portions of the surface effect vessel are lifted out of the water as the vessel rides over wave peaks. When air from the air cushion is lost, a larger portion of the vessel's hull comes into contact with the water's surface. This air loss results in dramatically increased friction between the vessel and the water and causes the vessel to slow down or lurch. Thus, maintaining the low friction air cushion beneath a vessel's hull under adverse conditions is an important aspect of the design of surface effect vessels.
One prior art approach to maintaining the air cushion utilizes a flexible skirt positioned around the edges of the boat hull to help contain the air cushion. An example of such an embodiment is a hovercraft. Unfortunately, the flexible skirts used in these types of applications increase the resistance of the vessel through contact with the water's surface. In addition, these flexible skirts require extensive and expensive maintenance. Furthermore, these skirts are still prone to allow more air to escape from the air cushion in rough seas.
Yet another problem with prior art surface effect vessels is that their hulls are substantially planar in the area in front of the air cavity. The hull is constructed to be planar in the region in front of the air cavity to allow the air cushion to extend as far as possible to the sides of the vessel. However, at high speeds or in rough seas, this planar hull section will tend to ride up on wave peaks. The bouncing of the vessel results in a rough bumpy ride and decreased stability. In addition, as the planar hull section rises and falls in the heavy seas, air tends to vent from the supporting air cushion. Therefore, what is needed is a surface effect vessel that is configured to operate in heavy seas.
V-shaped hulls are designed to provide an improved ride in rough water, as compared to relatively flat hulls, by deflecting wave energy away from and to the sides of the hull. Thus, traditional V-shaped hulls provide improved ride qualities at the expense of low speed planing and fuel efficiency. However, if the hull of a surface effect ship is made a moderate to deep V-shape, air from the air cushion tends to vent from the sides of the V-shaped hull when the vessel's speed increases and the edges of the V-shaped hull rise out of the water. Thus, prior art surface effect vessels have not utilized deep-V hulls. Therefore, what is needed is a deep-V hull configuration for a surface effect vessel that provides improved high speed handling characteristics without substantially increasing the amount of air venting from the air cushion.